A new systematic review published in the International Journal of Obesity looks at the totality of evidence investigating whether consuming low energy sweeteners (LES), such as aspartame, sucralose, or stevia, is a net benefit or detriment for weight control. In addition to providing some clarity on the answer, the review also provides some insight into how different kinds of evidence address such questions.

LES vs sugar or water

The question may at first seem obvious – if you consume a beverage sweetened with an LES instead of sugar you will be avoiding up to several hundred calories. Those calories add up quickly. Twelve ounces of cola with sugar has 138 calories, for example. These are foods that people generally consume on a daily basis, and so avoiding these unnecessary calories should reduce total energy intake and help reduce or maintain weight.

The human body, however, is a complex system, as is human psychology, and so we have to consider the law of unintended consequences. It is possible, for example, that when people drink a diet beverage they feel they have earned the right to consume more calories elsewhere. This phenomenon is called compensation, and there is evidence for this effect.

The food industry is responsible for our increased sugar consumption because it puts hidden sugar in processed foods, bombards us with advertising, favors profits over health, and lobbies against regulation.

The government is responsible because it has failed to control the food industry.

The film has received mostly positive reviews and has been called the Inconvenient Truth of the health movement. It was written and directed by Stephanie Soechtig, whose earlier films attacked GMO foods and the bottled water industry, and narrated by Katie Couric, who “gave anti-vaccine ideas a shot” on her talk show in late 2013.

The film shows families struggling with childhood obesity and “experts” expressing their opinions. Their selection of “experts” is heavy on politicians and journalists and light on nutrition scientists.(more…)

Gary Taubes has written two books explaining why people get fat and why a low-carb diet is the solution to preventing and treating obesity. He didn’t like what I had to say about his books on this blog back in 2011. I was not the only one to criticize. Another reviewer accused him of “abandon[ing] journalistic and scientific integrity in place of observational data, straw men and logical fallacy.” He says he agrees with Taubes’ premises but that his “arguments made me cringe,” and he goes into considerable detail to explain why. His analysis is worth reading.

Rather than engaging in the Comments section, Taubes complained to me in a somewhat offensive personal e-mail, saying I had failed to understand what he wrote. Recently he e-mailed me again, condescendingly suggesting that I might understand his arguments better if I read an article he wrote last year for the British Medical Journal. I read it, and confirmed that I had understood perfectly well the first time around and that it was Gary Taubes who didn’t understand my criticisms. I pointed out some omissions and inconsistencies, but my major criticisms boiled down to two:

He strongly recommended that everyone adopt a low-carb diet, essentially insisting that we act on insufficient evidence. And this was after he had devoted whole chapters of his books to demonizing the low-fat diet advocates for doing exactly that: acting on insufficient evidence.

I’ve been aware of this issue for some time and had been thinking of blogging about it for at least three years. The reason is that the oncologist who is best known for sounding the alarm on this issue is Jennifer Griggs at the University of Michigan and, being local and all, I’ve seen her speak on the topic several times at local breast cancer conferences. Now that I work with a statewide breast cancer care quality improvement initiative, I’m becoming more aware of her work. Indeed, I was rather puzzled why this issue bubbled up enough to be reported widely on the national news last week when the Nature Clinical Oncology paper by Gary H. Lyman and Alex Sparreboom that drew attention to the issue was published in August, and the original American Society of Clinical Oncology (ASCO) guidelines were published last year. Whatever the reason this issue has been getting more attention, it’s a good thing.(more…)

In the past I have criticized evolutionary medicine for its tendency to rely on unverifiable “Just-So Stories,” but a new book has helped me appreciate what the best kind of evolutionary thinking can contribute to our understanding of medicine. Doves, Diplomats, and Diabetes: A Darwinian Interpretation of Type 2 Diabetes and Related Disorders by Milind Watve investigates diabetes from an evolutionary perspective, suggesting how it might have originated, why it persisted, and how it is related to survival advantages. Watve develops well-reasoned hypotheses that can be tested by examining their expected consequences. He believes it is impossible to understand metabolism without understanding behavioral ecology, and he makes a good case.

A reassessment of the evidence concerning Type II diabetes (T2D) reveals a number of paradoxes. Elevated blood glucose is the defining feature of T2D but controlling it doesn’t prevent all the complications of diabetes, and it doesn’t appear that elevated blood sugar could produce all the pathological changes of diabetes. Insulin resistance is believed to be central to a cluster of deadly diseases in humans, but in other animals it has no adverse effects on health and even increases lifespan. Studying diabetes from an evolutionary perspective can shed light on such paradoxes. (more…)

Being fat is bad except when it’s good. It’s called “the obesity paradox.” (No, that isn’t a mis-spelling for “two physicians who treat fat people.”) The adverse health effects of obesity are well established, but there are exceptions. Obesity appears to confer an advantage in certain subgroups with conditions like heart disease and diabetes.

In the News

Casual consumers of some recent media reports might interpret them as an excuse to stop trying to lose excess weight, especially if they are diabetic. Others might think we have been lied to about the dangers of the obesity epidemic. The reality is more complicated. (more…)

A number of buzz-words appear repeatedly in health claims, such as natural, antioxidants, organic, and inflammation. Inflammation has been implicated in a number of chronic diseases, including diabetes, Parkinson’s, rheumatoid arthritis, allergies, atherosclerosis, and even cancer. Inflammation has been demonized, and is usually thought of as a bad thing. But it is not all bad.

In a study in Nature Medicine in September 2011, a research group led by Dr. Umut Ozcan at Children’s Hospital Boston (a teaching hospital affiliated with Harvard Medical School) reported that two proteins activated by inflammation are crucial to maintaining normal blood sugar levels in obese and diabetic mice. This could be the beginning of a new paradigm. Ozcan says:

This finding is completely contrary to the general dogma in the diabetes field that low-grade inflammation in obesity causes insulin resistance and type 2 diabetes. For 20 years, this inflammation has been seen as detrimental, whereas it is actually beneficial.

Increasing levels of these inflammatory signals might actually be therapeutic in diabetes and obesity. On the other hand, they might worsen inflammatory diseases like asthma and rheumatoid arthritis. Ozcan’s findings are intriguing and might eventually lead to new treatments, but there are no clinical applications as yet.

I recently received an e-mail from a high school science department head who is teaching a unit on nutritional science. He asked for my opinion of a YouTube video of a lecture advocating a high saturated fat diet. The speaker is Donald W. Miller, Jr., M.D., a cardiothoracic surgeon at my alma mater, the University of Washington. My correspondent commented, “I have a feeling that there is room for some skepticism.” I agree: there’s a whole lot of room for skepticism.

An article based on that video lecture is available on Dr. Miller’s website. It’s entitled “Enjoy Saturated Fats, They’re Good for You!” If you want to judge for yourselves, I recommend the article over the video, as he is a poor public speaker.

Dr. Miller’s website contains a lot of disturbing material. He appears to be a contrarian who disagrees with the consensus of scientific experts on a wide variety of topics, for instance:

Determining the net health effects of independent factors can be tricky, especially when those factors cannot be controlled for in experimental studies. For things like body mass index (BMI) we must rely on observational data and triangulate with multiple studies to isolate the contributions from BMI. But it can be done.

The data, however, are likely to be complex and noisy, and therefore there is plenty of opportunity for ideology to trump objectivity in interpreting the data. There are those who, for whatever reason, deny that we are having an obesity epidemic in the West, and those who deny the health implications of being overweight as an independent factor.

BMI

The terms overweight and obesity have had various definitions in the past, but in recent years the various health organizations have settled on consensus operational definitions (for obvious practical reasons). Their definition relates to body mass index, which is a person’s weight in kilograms (kg) divided by their height in meters (m) squared.

Carbohydrates are the cause of obesity and are also important causes of heart disease, type 2 diabetes, cancer, Alzheimer’s, and most of the so-called diseases of civilization.

A low-fat diet is not healthy.

A low-carb diet is essential both for weight loss and for health.

Dieters can satisfy their hunger pangs and eat as much as they want and still lose weight as long as they restrict carbohydrates.

He supports his thesis with data from the scientific literature and with persuasive theoretical arguments about insulin, blood sugar levels, glycemic index, insulin resistance, fat storage, inflammation, the metabolic syndrome, and other details of metabolism. Many readers will come away convinced that all we need to do to eliminate obesity, heart disease and many other diseases is to get people to limit carbohydrates in their diet. I’m not convinced, because I can see some flaws in his reasoning. (more…)